There are many processes for creating thin films, and these methods were developed to meet the manufacturing needs of specific technologies. For example, existing solution coating technologies such as slot die, curtain, and knife coating are able to manufacture thin films with high throughput. These techniques were designed for creating high quality films in continuous single sheets. These techniques, however, have a limited ability to create patterns.
Slot die coating is a method of creating thin films on a substrate from liquid materials. The essence of the process is a die consisting of two halves separated by a shim, with a pressurized reservoir, or chamber, machined into one of the halves containing fluid. The purpose of the shim is to create a gap between the two halves through which the fluid may flow. The purpose of the chamber is to uniformly distribute the fluid therein along the width of the gap. As a result, slot die designs are generally limited to lines or stripes that are the opening of the shim, thereby limiting the ability of the slot die to create other desired patterns.
Unlike solution coating, which is a continuous process, printing technology is designed to deposit material when and where it is needed. The principle of an inkjet process is that, based on an input pattern such as a body of text or an electronic circuit, a nozzle moves to a predetermined location and deposits solution. Deposition is obtained via digital command and resulting actuation of a jet dispensing mechanism. Inkjet printing is a process in which the product (line, film, etc.) consists of a buildup of individual ink droplets. Because deposition of the fluid can be precisely controlled, ink jet printing is capable of and excels at making films with sophisticated patterns. The buildup nature, however, does not produce as continuous or high quality a film as an extrusion process does. Moreover, ink jet printing suffers from low throughput capacity.
Another thin film production technique with high throughput is gravure printing. The basic operation for this process is a drum with a pattern of voids etched into it. Ink is fed into the voids and deposited on a substrate via pressure between the drum and the substrate. Like slot die coating, however, this process provides no customization of extruded patterns.
Today, there are emergent technologies such as organic electronics, battery electrodes, and radio frequency identification tags that would benefit from thin film manufacturing. While such emergent technologies use materials that are compatible with the aforementioned high throughput coating methods, they require patterning of films. These technologies, therefore, are largely restricted to ink jet printing and vapor deposition methods. This is partially because the required patterns are too sophisticated for processes such as gravure printing and slot die, knife and spray coating without the inclusion of multiple secondary operations that are detrimental to throughput.
A key enabling development for the emergent technologies would be suitable manufacturing processes that provide high production capacity and coating of thin films in continuous discrete and non-discrete patterns. Modified slot die coating has been shown to be an ideal technology to coat printed lines; however, a major limitation of the modified slot die coating process is the lack of a dynamic, direct patterning. More specifically, it is a static process that does not allow for programmed input of coating patterns. Other high throughput methods used to coat patterns also suffer from being static systems or requiring intricate material removal steps and are often expensive.
Patterned thin films that can be produced rapidly with good uniformity are useful in emerging technologies. A need exists for a dynamic, customizable patterning process for thin film production having high throughput and optimization of patterns without increasing manufacturing costs.